.\" $OpenBSD: X509_LOOKUP_hash_dir.3,v 1.9 2019/06/06 01:06:59 schwarze Exp $
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.Dd $Mdocdate: June 6 2019 $
.Dt X509_LOOKUP_HASH_DIR 3
.Os
.Sh NAME
.Nm X509_LOOKUP_hash_dir ,
.Nm X509_LOOKUP_file ,
.Nm X509_load_cert_file ,
.Nm X509_load_crl_file ,
.Nm X509_load_cert_crl_file
.Nd default OpenSSL certificate lookup methods
.Sh SYNOPSIS
.In openssl/x509_vfy.h
.Ft X509_LOOKUP_METHOD *
.Fn X509_LOOKUP_hash_dir void
.Ft X509_LOOKUP_METHOD *
.Fn X509_LOOKUP_file void
.Ft int
.Fo X509_load_cert_file
.Fa "X509_LOOKUP *ctx"
.Fa "const char *file"
.Fa "int type"
.Fc
.Ft int
.Fo X509_load_crl_file
.Fa "X509_LOOKUP *ctx"
.Fa "const char *file"
.Fa "int type"
.Fc
.Ft int
.Fo X509_load_cert_crl_file
.Fa "X509_LOOKUP *ctx"
.Fa "const char *file"
.Fa "int type"
.Fc
.Sh DESCRIPTION
.Fn X509_LOOKUP_hash_dir
and
.Fn X509_LOOKUP_file
are two certificate lookup methods to use with
.Vt X509_STORE ,
provided by the OpenSSL library.
.Pp
Users of the library typically do not need to create instances of these
methods manually.
They are created automatically by the
.Xr X509_STORE_load_locations 3
or
.Xr SSL_CTX_load_verify_locations 3
functions.
.Pp
Internally, loading of certificates and CRLs is implemented via the functions
.Fn X509_load_cert_crl_file ,
.Fn X509_load_cert_file
and
.Fn X509_load_crl_file .
These functions support a parameter
.Fa type ,
which can be one of the constants
.Dv FILETYPE_PEM ,
.Dv FILETYPE_ASN1 ,
and
.Dv FILETYPE_DEFAULT .
They load certificates and/or CRLs from the specified file into a
memory cache of
.Vt X509_STORE
objects which the given
.Fa ctx
parameter is associated with.
.Pp
The functions
.Fn X509_load_cert_file
and
.Fn X509_load_crl_file
can load both PEM and DER formats depending on the
.Fa type
value.
Because DER format cannot contain more than one certificate or CRL
object (while PEM can contain several concatenated PEM objects),
.Fn X509_load_cert_crl_file
with
.Dv FILETYPE_ASN1
is equivalent to
.Fn X509_load_cert_file .
.Pp
The constant
.Dv FILETYPE_DEFAULT
with
.Dv NULL
filename causes these functions to load the default certificate
store file (see
.Xr X509_STORE_set_default_paths 3 ) .
.Pp
Both methods support adding several certificate locations into one
.Sy X509_STORE .
.Pp
This page documents certificate store formats used by these methods and
caching policy.
.Ss File Method
The
.Fn X509_LOOKUP_file
method loads all the certificates or CRLs present in a file into memory
at the time the file is added as a lookup source.
.Pp
The file format is ASCII text which contains concatenated PEM
certificates and CRLs.
.Pp
This method should be used by applications which work with a small set
of CAs.
.Ss Hashed Directory Method
.Fa X509_LOOKUP_hash_dir
is a more advanced method which loads certificates and CRLs on demand,
and caches them in memory once they are loaded.
As of OpenSSL 1.0.0, it also checks for newer CRLs upon each lookup, so
that newer CRLs are used as soon as they appear in the directory.
.Pp
The directory should contain one certificate or CRL per file in PEM
format, with a file name of the form
.Ar hash . Ns Ar N
for a certificate, or
.Ar hash . Ns Sy r Ns Ar N
for a CRL.
The
.Ar hash
is the value returned by the
.Xr X509_NAME_hash 3
function applied to the subject name for certificates or issuer
name for CRLs.
The hash can also be obtained via the
.Fl hash
option of the
.Xr openssl 1
.Cm x509
or
.Cm crl
commands.
.Pp
The
.Ar N
suffix is a sequence number that starts at zero and is incremented
consecutively for each certificate or CRL with the same
.Ar hash
value.
Gaps in the sequence numbers are not supported.
It is assumed that there are no more objects with the same hash
beyond the first missing number in the sequence.
.Pp
Sequence numbers make it possible for the directory to contain multiple
certificates with the same subject name hash value.
For example, it is possible to have in the store several certificates
with the same subject or several CRLs with the same issuer (and, for
example, a different validity period).
.Pp
When checking for new CRLs, once one CRL for a given hash value is
loaded, hash_dir lookup method checks only for certificates with
sequence number greater than that of the already cached CRL.
.Pp
Note that the hash algorithm used for subject name hashing changed in
OpenSSL 1.0.0, and all certificate stores have to be rehashed when
moving from OpenSSL 0.9.8 to 1.0.0.
.Sh RETURN VALUES
.Fn X509_LOOKUP_hash_dir
and
.Fn X509_LOOKUP_file
always return a pointer to a static
.Vt X509_LOOKUP_METHOD
structure.
.Pp
.Fn X509_load_cert_file ,
.Fn X509_load_crl_file ,
and
.Fn X509_load_cert_crl_file
return the number of objects loaded from the
.Fa file
or 0 on error.
.Sh SEE ALSO
.Xr d2i_X509_bio 3 ,
.Xr PEM_read_PrivateKey 3 ,
.Xr SSL_CTX_load_verify_locations 3 ,
.Xr X509_OBJECT_get0_X509 3 ,
.Xr X509_STORE_load_locations 3 ,
.Xr X509_STORE_new 3
.Sh HISTORY
.Fn X509_LOOKUP_hash_dir ,
.Fn X509_LOOKUP_file ,
and
.Fn X509_load_cert_file
first appeared in SSLeay 0.8.0.
.Fn X509_load_crl_file
first appeared in SSLeay 0.9.0.
These functions have been available since
.Ox 2.4 .
.Pp
.Fn X509_load_cert_crl_file
first appeared in OpenSSL 0.9.5 and has been available since
.Ox 2.7 .
